Headlight intensity tester



G. M GRAHAM HEADLIGHT INTENS I TY TESTER March 7, 1939.

a Sheets-Sheet 1 Fi1e d July 31, 1936' March 7, 1939. G. M4 GRAHAM HEADLIGHT INTENSITY TESTER Filed July :51, 1936 s Sheets-Sheet 2 I NV ENT OR. GEUQEEMEQAHA/v ATTORNEY.

March], 1939.. G, M, R AM 2,149,285

HEADLIGHT INTENSITY TESTER Filed J u1 51, 19 36 3 Sheets-Sheet s INVENTOR. EE'UHEEMERKHAM ATTORNEY.

Patented 7, $39

UNITED STATES. PATENT OFFICE l I 2.14m;

nasnuonrmmsrrr mam George M. Graham, Detroit, m, alignor a marries... Application July :1, 1m, Serial No. 03,006

' 5 Claims. (01. ss-zs) This invention relates to an apparatus for testing the headlights of a motor vehicle.

Hithertoiore it has been the practice to employ devices for measuring the efllciency of headlights I which were not capable of testing dlilerent kinds or types of headlights nor adjustable for certain factors which indirectly aflfected headlight illumination. These devices were usually large, awkward and relatively expensive to manufacture.

0 Furthermore, it has been the practice to measure the intensity of headlight illumination without any consideration for the voltage of the circuit producing such illumination. It is well known that the voltage of the headlight circuit varies from time to time depending upon the conditions under'which the motorvehicle is driven and that these variations alter the illumination of the headlights. When considerable driving is done in the day time, the voltage of the battery in the motor vehicle is normally increased. The reverse is true, if considerable amount of driving is done at night under self-illumination. Variations in the voltage of the headlight circuit produce corresponding fluctuations in headlight illumination. The methods pursued in the past failed to take into consideration the voltage factor and accordingly the results obtained were approximate and subject at times to considerable error.

An important object of this invention is to provide a small, compact, accurate measuring device or instrument for measuring the light efliciencies of motor vehicle headlights. The device is readily adaptable to different kinds and makes of headlights; In accomplishing its purpose, the device is as provided with novel means fqncompensating for voltage irregularities in the headlight circuit. In addition, the device is designed in -an improved manner for measuring all standard candlepowers of headlight lamps. These .features are all combined in a single, compact, portable instrument which is easily adjusted for all conditions encountered in headlight illumination tests .of this character.

Exact results are important in headlight illumination tests. These tests are usually conducted directly in front of the headlights andsmall discrepancies in headlight illumination at this point make big differences in the condition of the illumination many feet in front of the vehicle. I find thereforethat the procedure of ascertaining the voltage of the headlight 'i rcuit and compensating for any irregularities in e voltage is important. Tests of this character cannot be accurate if this consideration is neglected. In addition to thls'I the step of collecting substantially all the rays issuing from the headlight and measuring the lightjintensity of all the rays and not a portion thereof. This last step in combination with the step of compensating for voltage irregularities provides a method for measuring headlight illumination which is both accurate'and novel. All factors of headlight illumination, such as the voltage of the headlight circuit and the peculiarities of headlight lenses, are considered by this method of lo measuring the efficiencies of headlights.

Other features of the invention are of importance. One such feature is the provision of a light sensitive circuit for measuring headlight eflicienc'y and'including a light sensitive element 1 adapted to generate an electric current in proportion to the amount of light received thereon. The circuit is arranged in a novel manner for measuring both the candlepower of the headlight beam and the voltage of the headlight circuit. Another 20 such feature is the provision of a dial and asso- 'ciated mechanism which is adapted to register the percentage eiiiciency of the headlight beam or the voltage of the headlight circuit depending upon the manner in which the device is associated with 26 the headlight. Novel means is provided for compensating the circuit of the headlight tester for irregularities in the voltage of the headlight cir- -cuit so that all headlights are measured against a common standard and irrespective of what the voltages of their circuits are. In addition to these features, the device is provided with a plurality of novel elements for electrically connecting the device into the circuit of the headlight. These elements are readily adaptable to all conditions Y and kinds of headlights.

Various other objects, advantages and meritorious features will become apparent from the following speciiication, appended claims and accompanying drawings, wherein: 40

Fig. 1 is a view illustrating one position assumed in measuring the light eiiiciency of a headlight of a motor vehicle. V

Fig. 2 is a side view of the headlight testing a instrument showing in dotted outline the interior construction of the instrument,

ment for headlights of diiferent standard candle- 5o powers, J

Fig. 4 is a rear end view of the instrument along linel-lofFigJ, Fig. 5 is an enlarged view of the dial. provided on the instrument showing a pointer and scales for age,

Fig. 6 is a view of the end of the electric cord attached to the instrument showing one manner of electrically connecting the instrument into the circuit of the headlight,

Fig.7 is a diagrammatic view illustrating one embodiment of the invention and one manner of connecting the circuit of the instrument into the circuit of the headlight,

Fig. 8 is a view similar to Fig. 7 showing one manner of testing the light beam of a headlight,

Fig. 9 is a diagrammatic view illustrating another embodiment of the invention and showing another manner of connecting the circuit of the device into the circuit of the headlight.

fig. 10 is a view illustrating another position which may be assumed ior measuring the light efiiciency of a headlight and showing one manner for condensing the light rays of the headlight so that all are collected and measured,

Fig. 11 is a side view of a modified form of the device for testing headlight illumination,

Fig. 12 is a front end view of the device in Fig. 11 showing a construction for admitting various amounts of light to the light sensitive element in the device.

Fig. 13 is a side view of one electrical'contact device which may be employed with the terminal plug shown in Fig. 6, and

Fig. la is a side view of another electrical con-'- tact which may be employed with the terminal plug shown in Fig. 6.

Referring in more detail to the drawings Figs. 1 and 10 illustrate two ways of positioning the headlight testing instrument in front of a headlight of a motor vehicle. The motor vehicle is indicated at M. The vehicle supports in the usual way a headlight l 2 having a lens M, a lamp is and a reflector is disposed about the lamp and acting to converge the rays of light emitted by the lamp into a beam in the customary manner.

The headlight testing instrument is housed within a suitable casing or container 201 which may be shaped as illustrated in Figs. 2, 3, and 4. The front end of the casing is provided with an aperture 22 through which light is admitted to the interior of the casing. The top inclined wall of the instrument is provided with a dial 24 comprising a light efllciency scale 26, a voltage scale with a channel 32 formed by two spaced metal I elements 34 each of which is secured to a projecting rib 36 so as to overhang the space between the ribs and form the channel as readily appre- The amount of light entering the hole 22 may be governed by an opaque member or disc 40 having a plurality of apertures 42, 44 and 46 of varying diameters. Instead of controlling the amount of light admitted in this manner, glass filters of varying light penetrating qualities may be arranged to pass in front of the hole 22. as will be more fully described hereinafter. A knob dd may be provided for rotating the disc about the pivotal center 50. The apertures 42, M and at are calibrated in accordance wlththe various candlepowers of standard lamps customarily employed in headlights. The smallest aperture d2 is intended to admit light to the instrument when the latter is used for testing headlights containing a standard lamp of the highest candlepower. The largest aperture 56 is intended to admit light to the instrument when the latter is used for testing headlights co'ntaining a standard lamp of the smallest standard candlepower. Various apertures intermediate these extreme sizes may be used when measuring headlights containing lamps of intermediate power and one such aper ture 3 3 is shown. The candlepowers most gen-- erally used for headlight lamps are 21, 32 and 50 and the sizes of the apertures in disc Ht can be calibrated in the manner described above in accordance with these candlepowers. Theseapertures should be so proportioned relative to one another that each will admit the same amount of light from a correctly shining lamp of the candlepower for which they are intended. Comparative tests of headlights can then be made irrespective of the various standard candlepowers at which the lamps in the headlights may shine.

In order to electrically connect the instrument into the circuit of the headlight to ascertain the voltage thereof and make compensation therefor, there is provided a double wire electric cord 52 to. the end of which is fixed a terminal plug M. This terminal plug is arranged to detachably receive any type of electrical contact mechanism in the manner indicated in Fig. 6. The electricalcontact mechanisms receivable on the end of plug 54 are constructed similarly to the lamp bases used for securing the lamps in the headlights. These bases are of various designs depending upon the headlight construction and for that reason provision is made on theplug 54 for receiving various types of contacts. Two forms of electrical contact mechanisms are shown at 56 and 58 in Figs. 13 and 14 respectively. The left hand portions of each of these mechanisms are constructed exactly like the lamp bases of two standard headlight lamps. Obviously other types of contact devices can be fitted upon the plug 54.

A variable resistance or rheostat is provided in the instrument. The handle for adjusting the rheostat extends from the-top wall of the instrument adjacent the dial 24 and is indicated at 60.

The interior construction of the device is generally shown by the dotted lines in Fig. 2. It

. comprises a light sensitive element 62 disposed across the opening 22. The rheostat is generally indicated at 64. A fixed high electrical resistance is indicated at 65. A current meter for operating the pointer 30 is generally indicated at 68.

Two circuits for operating the parts of the instrur'nent hereinabove described are illustrated diagrammatically in Figs. 7, 8 and 9. Similar parts are designated throughout these figures with similar reference numerals. In Figs. '7 and 8 the light sensitive element 62 generates a minute current in proportion to the light received thereon. The circuit I carries this current through a switch 12 and the variable resistance 8 is adapted to employ the double wire electric instrument and adjusted in the same manner as the previously described rheostat 84. From cord I2 previously described. This cord'is diagrammatically shown in Figs. 7 and 8 as connected into the circuit II on opposite sides of the when connected to the circuit of the headlight.

This dual use reduces the number of parts and enables a compact and easily readable instrument to be provided.

Switch 12 can be operatively associated with the rheostat handle ill in any suitable way so that when the rheostat is functioning as a variable resistor it will connect circuit 52 with the meter 24 but at one extreme position of its movement the handle can be arranged to cut out circuit 52 and connect the circuit III with the meter. Comparison of Figs. 7 and 8 shows the different positions assumed by switch 12 during the test.

In Fig. 'l the plug 54 on the end of the cord 52 is shown being attached to the lamp socket of the headlight. The circuit for the headlight including the battery 14 of the motor. vehicle is shown at 15. In Fig.8 headlight lamp l6 and the lens i4 have been replaced and the beam emitted by the headlight is received upon the element 82. The embodiment in Figs. '1 and 8 requires the removal of the headlight .lens and lamp and plugging the cord 52 into the lamp circuit in order to ascertain the voltage of the headlight circuit and make compensation therefor. After the cord has been secured to thesocket of the headlight lamp, the rheostat 64 is adjusted until the pointer 30 swings a certain prescribed distance, which distance of movement is intended to be used in all measurements. This distance may be indicated by the 5% volts designation on scale 28. After the rheostat has been adjusted so that the pointer swings to this reference, the cord is disconnected from the lamp socket and the lamp and lens are replaced. The beam of light thrown by the headlight is then caught upon the element 62 and the percentage efficiency of the beam is indicated on scale 26.

In Fig. 9 there -is shown a circuit diagram which does not require the removal of the heada light lamp and lens. Instead provision is made for introducing into the headlight circuit a variable resistance for varying the effective voltage of the headlight circuit at the lamp socket. The electric meter 68 is adapted to be connected either into the headlight circuit or into the circuit of the element 62 by a. switch Referring in detail to Fig. 9 the circuit 18 be- 1 tween the element 62 and the meter 24 is substantially like that in Figs. 7 and 8 except for the position of a switch I8. In place of the electric cord circuit I2, there is provideda device ll which is arranged to be introduced into the headlight circuit between the battery 14 and theheadlight lamp. This device maybe introduced into the headlight circuit just before the headlight as shown in Fig. 9, and certain types of headlights are constructed so that such a connection is readily made. The device is provided with a circuit 82 which carries the current of the headlight circuit to a variable rmistance I4. This variable resistance can be located in the same place in the apertures of varyi thence the current is returned to the headlight circuit where it is used to light the lamp. The

device 80 is provided with a branch circuit 86 which runs to the circuit of the element 62 through a fixed high resistance It. This last resistance functions in the same manner as the fixed resitance 88 previously described. The switch I8 is arranged to connect the meter 68 into either the circuit of the element 62 or the circuit of the device 80. as is readily understood from Fig. 9.

.The operation of the embodiment in'Fig. 9 is readily perceived. 'After the device 80 is introduced into the headlight circuit, the switch 18 is swung to connect the meter to the circuit 82 of this device. The high resistance 88 enables the meter to function as a voltmeter, and by varying the variable resistance 84 the resistance of the headlight circuit can be varied while the connect the meter with either the headlight circuit or the light sensitive element.

In Figs. 10, 11 and 12 I have shown a modification of the invention wherein all of the light beam is collected upon the light sensitive element .62 and wherein novel means is provided for detachably connecting the light testing instrument to the circuit of the motor vehicle preferably on the battery side of the headlight circuit. The instrument is constructed substantially like that described in Figs. 1 to 8, inclusive, with the exception of a few features which will be pointed out and specifically described hereinafter. The

' instrument is slidablysupported upon the bar 38 as in Fig. 1 but a convex lens 90, which may form a part of the equipment described in my above mentioned copending application, is interposed between the headlight and the instrument. This lens is of such a size as to collect substantially all the light emitted by the headlight and condense it upon the light sensitive element provided in the instrument..

The-ends of the wires in the electric cord 92 in opening and closing the circuit to the instrument.

I Instead of providinga disc with a series of sizes, the opening through which the light beam is directed may be covered with suitable neutral light filters of varying strengths. Such a construction is illustrated in -Figs. 11 and 12. A light filter "I0 is fixed in the opening of the instrument in front of the light sensitive element. The percentage efilciencyscale is calibrated in connection with this filter so as to give the percentage efficiency of either the low or medium candlepowers of standard headlight lamps.

The greater majority of the motor vehicles of today use a headlight lamp of 32 candlepower.

The percentage efilciency scale can be calibrated in connection with the filter I00 to register the efficiency of such a headlight lamp, or if desired it can be calibrated to give the percentage efllciency of a standard lamp of less candlepower. In either case, an additional light filter may be provided for lamps of different candlepower. One such filter is designated at I02 mounted within a frame I04 pivoted at I06 to the outside of the casing. This filter is arranged to swing in front of the opening and superimpose the filter I02. Both filters act together to' cut down the light entering the instrument and allow the instrument to be used for standard lamps of higher candlepower. Obviously any number of swingable filters may be employed for any candlepowers measured. A thin fiat metal disc I08 is likewise pivotally secured to the casing and is arranged to superimpose all the filters when the latter are assembled in front of the opening and in this way protect these parts against breakage.

The apparatus described in Figs. 10 to 12, in-- clusive, is first assembled as shown in Fig. 10 with the lens 90 interposed between the headlight and the light testing instrument. The position of the instrument on the bar 30 should be adjusted until all the light rays condensed by the lens enter the opening in the instrument. The clamps 93 are tapped into the circuit of the motor vehicle at any accessible place but preferably before the headlight circuit. Switch 98 isturned on. If the circuit described in Figs. '7 and 8 is employed, the rheostat handle is turned so that switch I2 connects the circuit 92 with the current meter in the instrument. The voltage of the motor vehicle circuit will register on the dial and this can be adjusted to a zero reading such as to 5 volts by turning the rheostat handle.

If a standard 32 candlepower lamp. is used in the headlight, only the one light filter I00 need be used. The others may 'be'tumed away from the opening 22 of the instrument if this is the case. After compensation for the voltage of the motor vehicle battery has been made, the 'rheostat handle is turned to one of its extreme positions when it will disconnect the circuit 92 and connect the element 62 with the current meter 68. The percentage efficiency of the headlight beam will be indicated by the pointer 30 on scale 26. The reading will denote the efllciency of substantially the whole. beam of light emitted by the headlight and irrespective of irregularities in the battery circuit.

If a poor efiiciency reading is obtained, the.

cause may reside in the lamp bu'lb or the relationship between the lamp bulb and the reflector Ill. The headlight'circuit may be at fault and such a condition can be ascertained, if desired, by electrically connecting the light testing instrument by means of an electric cord 92 to the battery side of the headlight circuit and then to the lamp bulb side. If a variation in the readings occur when such steps are made, then a cause of the eating the usual voltages of a headlight circuit, a compound circuit for said meter including a branch circuit having a light sensitive electric element adapted to generate an electric current in proportion to the light received thereon and a second branch circuit including a high resistance and means for detachably connecting this branch circuit into the headlight circuit of an automobile, and means for selectively alternately electrically connecting the meter to either the branch circuit of said element or the branch circuit including said headlight circuit attaching means, the pointer adapted in the first mode of connection to indicate the light intensity of a headlight on the light intensity scale and in the second mode of connection to indicate the voltage of the headlight circuit on the voltage scale.

2. The invention described in claim 1 characterized by the fact that a variable electric resistance means is provided in said compound circult to compensate for voltage irregularities in the automobile headlight circuit subjected to the test.

3. A device for testing headlights of an automobile comprising, in combination, an electric circuit including alight sensitive element adapted to generate an electric current in proportion to the intensity of light received thereon and means for detachably connecting the circuit across the headlight circuit of an automobile, an electric meter havinga scale for indicating the intensity of automobile headlight beamsand a scale for -indicating voltages of an automobilezheadlight circuit, said meter also having a single movable pointer adapted to move past said scales and register either the light intensity of a headlight beam or the voltage of a headlight circuit, and switch means comprising a single movable element adapted in one position of its movement to electrically connect the meter and the light sensitive element in a closed circuit'excluding the detachable connecting means and in another position of its movement to-exclude the light sensitive element and electrically connect the meter and the detachable connecting means together so that when the latter is connected across an automobile headlight circuit the meter will receive current therefrom, said'pointer in the first instance adapted to measure the headlight beam lintensity of an automobile headlight when the beam thereof is directed upon said sensitive element and in the second instance to measure the voltage of a headlight circuit when the detachable connecting means are electrically connected across an automobile headlight circuit, and means for compensating in the readings of the headlight beam intensity scale for differences in the voltages of the circuits of the headlights tested.

4. An. electric device for testing headlights of an automobile comprising, in combination, a

light sensitiveelement adapted to generate an electric current in proportion to the intensity'of light received thereon, a pair of electric leads having means on one end of each lead for electrically connecting the same in the circuitof a headlight, one of said leads having an unbroken electrical connection with said light sensitive element, the other lead including a relatively high ill amazes nently connected with said lead which extends unbrokenly from said light sensitive element, the other meter lead connected to a switch comprising a single movable element which element is adapted in' one position to electrically connect the meter lead to the side of said lightsensitive element opposite that from which said unbroken lead extends and in another position to electrically connect the meter lead to the lead containing the electrical resistance, said meter adapted in the first form of switch connection to indicate by means of the pointer the light intensity of a headlight beam directed upon said light sensitive element and in the second form or switch con nection to indicate 'by means oi the pointer the voltage of a headlight circuit across which said first mentioned pair of leads may be connected.

5. A device for testing headlights of an automobile comprising, in combination, an electric circuit including alight sensitive element adapted to generate an electric current in proportion to the intensity of light received thereon and means for detachably connecting the circuit across the headlight circuit of an automobile, an electric meter having a scale for indicating the intensity of automobile headlight beams and a scale for indicating voltages of an automobile headlight circuit, said meter also having a single movable pointer adapted to move past said scales and register either the light intensity of a headlight beam or the voltage of a headlight circuit, and switch means comprising a single movable element adapted in one position of its movement to electrically connect the meter and the light sensitive element in a closed circuit excluding the detachable connecting means and in another position of its movement to exclude the light sensitive element and electrically connect the meter and .the detachable connecting means together so that when the latter'is connected across an automobile headlight circuit the meter will receive current therefrom, said pointer in the first instance adapted to measure the headlight beam intensity of an automobile headlight when the beam there- 01 is directed upon said sensitive element and in the second instance to measure the voltage of a headlight circuit when the detachable connect- -ing means are electrically connected across an automobile headlight circuit.

GEORGE M. GRAHAM. 

